The main aim of the proposed projects is to investigate the role that the central noradrenergic system, located in the locus coeruleus (LC), exerts in the static and dynamic control of posture and movements. It was previously shown that the LC exerts a facilitatory influence on posture either directly, by utilizing the facilitatory coeruleospinal (CS) pathway or indirectly, by suppressing the discharge of dorsal pontine reticular formation (pRF) neurons and the related medullary inhibitory reticulospinal (RS) system. Since CS as well as RS neurons respond to sinusoidal stimulation of labyrinth receptors, thus intervening in the gain regulation of vestibulospinal (VS) reflexes, experiments will be performed in decerebrate cats to identify the role that putative excitatory (or inhibitory) neurotransmitters and neuromodulators, locally applied within the LC, exert on posture as well as on the gain of VS reflexes. A second series of experiments will be carried out in unanaesthetized cats to find out whether changes in the background discharge of LC neurons and/or the related pRF neurons, induced by local injection of appropriate neurotransmitter-agonists, may modify the amplitude of the postural adjustments which occur during the forelimb flexion elicited by unilateral stimulation of the corresponding motor cortex, without affecting the limb movement. In addition to descending projections to the spinal cord, the LC sends afferent projection to the cerebellum. Experiments will be performed to investigate whether changes in the activity of the noradrenergic afferent projections ending either within the cerebellar vermis or within the flocculus may modify the gain of the VS reflexes in decerebrate cats, as well as the adaptive changes in the vestibulo-ocular reflexes (VOR) gain normally occurring in unanaesthetized rabbits.